I would stick in the beige family and redo the floor.

Then, I would get a pretty shower curtain, something solid, and keep it closed.

first of all, I think you should set a tub surround because water will hit the wall, and to avoid mold try to use it , you can read about it more https://bathroomer.org/tub-surrounds/ , I think it explains it better

If you make the easy change--the wall paint-- you can then accessorize with about any color you prefer. The tile is pretty basic neutral. Celebrate it--it could be a COLOR you are stuck with. When you choose lighting think about need in a bathroom; make up, shaving up lights won't be helpful. Be glad you don't have a 'tub surround' and have the actual tile!! It's not a huge space I think a large bath-mat would cover the gray flooring for you.

I don’t think painting the wall tile white will make much of a difference. The biggest impact will be a new vanity and when gutting bathroom down the road, just design around it.

Floor wise, an easy distraction is adding a large vinyl mat or even stencil it.

When choosing the mirror and lighting, as per vanity, select for long term. I‘d paint walls same color as tile so they won’t stand out, while nicer things will.

Look for a MCM style shower curtain that works with beige, brass and flooring to pull the whole look together.

You have nothing to lose as the more costly items can be incorporated into your new design when the time comes.

I think in your bathroom would need to toilet paper roll holder. i do not know where you put them now, but on the top WC there is a place where would look nice honeycomb or wave shape toilet paper holder what EWART WOODS ARE MAKING. Check maybe it it what you are looking for.